The present invention relates to the processing of substrates. More particularly, the present invention relates to improved techniques for liberating corrosive species from the chamber walls of a plasma processing chamber and/or the substrate surface. The present invention also relates to improved techniques for weakening the layers of polymer that are formed above a substrate during plasma processing to facilitate ease of removal.
In the manufacture of semiconductor devices such as integrated circuits and/or flat panel displays from substrates, particularly when plasma-enhanced processing techniques are employed, corrosive etchants may be employed to etch through one or more layers of the layer stack of the substrate. For example, a corrosive etchant may be employed to etch a desired pattern through the metallization layer of the layer stack. As is known, the metallization layer is typically employed to electrically couple device components together. If the metallization layer comprises aluminum, for example, the etchant gas employed may represent, in one example, chlorine or bromine.
For ease of discussion, the remainder of the discussion will be made with reference to the etching of an aluminum metallization layer using corrosive etchants containing chlorine and/or bromine. It should be understood, however, that the inventive techniques herein address the problems caused by any corrosive etchant (whether or not chlorine and/or bromine and whether or not employed to etch through an aluminum layer, or even a metallization layer).
Although corrosive species such as chlorine and/or bromine are efficient at etching the aluminum metallization layer, there are adverse side effects associated with their use. For example, even after the plasma etching step that employs the chlorine and/or bromine species is terminated, some of the chlorine and/or bromine species may be adsorbed onto layers of the layer stack itself. The presence of adsorbed corrosive species, e.g., chlorine and/or bromine, on the layer stack may introduce undesirable contamination into subsequent process steps.
Further, the continued presence of adsorbed chlorine and/or bromine on parts of the metal layer, e.g., the metal features' side walls, may cause the metal features to continue to corrode long after the fabrication process is finished. The continued corrosion of the metal features may eventually damage these metal features, causing the resultant semiconductor device to prematurely fail.
Additionally, it has been observed that chlorine and/or bromine species may become adsorbed onto the chamber walls of the plasma processing chamber. The presence of accumulated chlorine and/or bromine species in the chamber may contaminate other process steps. For example, particles containing chlorine and/or bromine may flake off the chamber wall and contaminate the environment within the plasma processing chamber, which may in turn contaminate the substrate undergoing processing.
The adsorbed chlorine and/or bromine species may react with moisture within the plasma processing chamber to form corrosive acids, which may migrate to other parts of the plasma processing system. These corrosive acids may lodge themselves in various parts of the plasma processing system, contributing to the contamination problem. Over time, the corrosive acids may damage or even destroy parts of the plasma processing system, particularly parts which are susceptible to corrosion such as those containing iron.
In view of the foregoing, there are desired efficient and effective techniques for removing adsorbed corrosive species from the chamber wall of a plasma processing chamber and/or the substrate.